Active specific immunotherapy has great potential for the treatment of patients with malignant melanoma. In light of the important role that antibodies and CD4 T cells of the helper (Th) type play in the control of cancer growth, approaches to active immunotherapy with B and Th cell- defined antigens (Ags) need to be developed. Very few melanoma- associated B and Th Ags or Th peptides with vaccine potential have been identified thus far. Most of the B cell Ags were carbohydrates and, therefore, they did not elicit T-cell responses; the Th Ags usually were individual-specific, rendering their usefulness as vaccines for a broad population of patients questionable. The major goal of this project is to develop melanoma vaccines with high potential for inducing B and Th responses. We will isolate, identify and characterize melanoma-associated Ags recognized by B or Th cells from patients with clinical improvement after immunotherapy. Selected Ags may induce not only B and/or Th cells, but also cytolytic T lymphocyte (CTL) responses. B cells Ags will be identified using antibody phage display technology. Combinatorial Fab libraries derived from patients' B cells will be expressed on the surfaces of filamentous phages, and phages bind preferentially to melanoma cells versus other tumor and normal cells will be selected (Core B). The Ags defined by selected Fab will be identified and evaluated for expression of T-cell epitopes (most likely of Th2-type). Th peptides recognized by available and to be established (from patients with clinical improvement after immunotherapy) Th lines or clones against melanoma will be identified (Core B), with emphasis on Th1-type peptides as these peptides may induce not only Th1-type T cells, but also CTL. Tissue expression of peptide epitopes also will be evaluated (Core B). The proposed studies will open new approaches to immunotherapy of melanoma using Ags or peptides defined by B or Th cells. This project interacts with Projects in the common goal to identify melanoma- associated Ags with diagnostic, prognostic and/or therapeutic value.